Multi-mode receiver

ABSTRACT

A multi-mode receiver system for processing signals based on a plurality of systems is disclosed. Embodiments of the invention provide for a shared architecture for processing baseband signals corresponding to a plurality of systems.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a transceiver. More particularly,the invention relates to a multi-mode receiver system.

2. Related Art

Feature additions in portable transceivers, such as cellular handsets,have resulted in color displays, radio receiver capabilities (e.g., forlistening to music), Internet-access, among others. With the trend incellular handsets toward miniaturization, such additional features canconsume additional space and power and increase costs. Additionaloverhead to accommodate the above features and others typically resultsin a consumer choosing between a portable handset that providesadditional functionality at a premium price or that requires additionalattachments and/or devices that are bulky and make portability lessconvenient.

Therefore, it would be desirable to provide a portable transceiver thatprovides enhanced features without requiring significant additionaloverhead and/or cost.

SUMMARY OF THE INVENTION

Embodiments of the invention include a multi-mode receiver (MMR) systemthat uses a substantial portion of the code-division multiple access(CDMA) architecture for providing digital-broadcast satellite (DBS)system functionality. Embodiments of the invention provide a basebandsection configured to process a first baseband signal based on a firstsystem using baseband components, wherein the baseband section isfurther configured to process a second baseband signal based on a secondsystem using the baseband components.

Related methods of operation are also provided. Other systems, methods,features, and advantages of the invention will be or become apparent toone with skill in the art upon examination of the following figures anddetailed description. It is intended that all such additional systems,methods, and features, and advantages be included within thisdescription, be within the scope of the invention, and be protected bythe accompanying claims.

BRIEF DESCRIPTION OF THE FIGURES

Many aspects of the invention can be better understood with reference tothe following drawings. The components in the drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present invention. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a block diagram illustrating a simplified portable transceiverwith a multi-mode receiver (MMR) system.

FIG. 2 is a block diagram illustrating an analog baseband embodiment ofthe MMR system shown in FIG. 1.

FIGS. 3A-3B are graph diagrams illustrating the different filtercharacteristics for the embodiment shown in FIG. 2 for code-divisionmultiple access (CDMA) functionality and digital-broadcast satellite(DBS) functionality.

FIG. 4 is a block diagram illustrating a first digital basebandembodiment of the MMR system shown in FIG. 1.

FIG. 5 is a block diagram illustrating a second digital basebandembodiment of the MMR system shown in FIG. 1.

DETAILED DESCRIPTION

Embodiments of a multi-mode receiver (MMR) system for a portabletransceiver are disclosed. In general, the MMR system includes receiverfunctionality that uses much of the existing code-division multipleaccess (CDMA) architecture for providing functionality of a receiverdesigned and/or used for a digital-broadcast satellite (DBS) system(e.g., having a downlink frequency of approximately 2642.5 MHz and anapproximately 25 MHz downlink bandwidth), among other systems such asglobal-positioning satellite (GPS) and/or personal-communication service(PCS). For example, a user may desire listening to and/or downloadingstereo music between calls. The MMR system enables the download ofsatellite music using much of the CDMA architecture. The MMR systemadapts to the different systems by using filters and DC (direct current)offset correction elements that have switchable bandwidths. Hereinoperating in a CDMA, DBS, GPS, or PCS “mode” will be understood toinclude providing receiver functionality that is consistent with astand-alone receiver or transceiver that would be designed and/or usedfor that particular system or service. For example, providing receiverfunctionality can include providing frequency response characteristicscorresponding to the particular system or service, having compliancewith respective standards and protocols, etc. Thus, the MMR systemachieves at least dual functionality, or in general, multi-modefunctionality at minimal die size and external component cost.

Although described with particular reference to a portable transceiverthat uses a CDMA architecture to provide DBS receiver functionality, theMMR system can be used with GSM (global system for mobilecommunications), analog AMPS (Advanced Mobile Phone system), and/orarchitectures compliant to other standards to provide for DBS receiveror receiver functionality for other systems. The description thatfollows will describe the MMR system implemented in analog baseband anddigital baseband embodiments, although the MMR system is not limited tothese embodiments.

FIG. 1 is a block diagram illustrating a simplified portable transceiver100. The portable transceiver 100 includes a speaker 102, display 104,keyboard 106, and microphone 108, all connected to a baseband subsystem130. In a particular embodiment, the portable transceiver 100 can be,for example but not limited to, a portable telecommunication device suchas a mobile/cellular-type telephone. The speaker 102 and display 104receive signals from the baseband subsystem 130 via connections 110 and112, respectively, as known to those skilled in the art. Similarly, thekeyboard 106 and microphone 108 supply signals to the baseband subsystem130 via connections 114 and 116, respectively. The baseband subsystem130 includes a microprocessor (μP) 118, memory 120, analog circuitry122, and a digital signal processor (DSP) 124 in communication via bus128. Bus 128, although shown as a single bus, may be implemented usingmultiple busses connected as necessary among the subsystems within thebaseband subsystem 130. The microprocessor 118 and memory 120 providesignal timing, processing and storage functions for the portabletransceiver 100. Analog circuitry 122 provides analog processingfunctions for the signals within the baseband subsystem 130. Thebaseband subsystem 130 provides control signals to a radio frequency(RF) subsystem 144 via connection 134. Although shown as a singleconnection 134, the control signals may originate from the DSP 124and/or from the microprocessor 118, and are supplied to a variety ofpoints within the RF subsystem 144. For example, the DSP 124 ormicroprocessor 118 can send control signals to a multi-mode receiver(MMR) system 200, enabling the MMR system 200 to switch among DBS, CDMA,PCS, and/or GPS modes. It should be noted that, for simplicity, only thebasic components of the portable transceiver 100 are illustrated herein.

The baseband subsystem 130 also includes, in one embodiment, adigital-to-analog converter (DAC) 136. The DAC 136 also communicateswith the microprocessor 118, memory 120, analog circuitry 122, and/orDSP 124 via bus 128. The DAC 136 converts the digital communicationinformation within baseband subsystem 130 into an analog signal fortransmission to the RF subsystem 144 via connection 142.

The analog signal on connection 142 is modulated and converted atmodulator system 148, in cooperation with one or more components of theMMR system 200 (via connection 166), and provided over connection 154. Apower amplifier system (PAS) 180 amplifies the modulated signal(s) onconnection 154 to the appropriate power level for transmission viaconnection 162 to a duplexer-and-switch module 174. The transmit signalenergy is provided from the duplexer-and-switch module 174 to an antenna172.

Signals are received at the antenna 172, provided to theduplexer-and-switch module 174, and routed to one of severalsignal-processing paths of the MMR system 200 via connection 173. Itwill be appreciated by one having ordinary skill in the art that in afull-duplex transceiver, such as that used in CDMA, the simultaneoustransmit/receive signal is accomplished, in one implementation, throughthe use of the duplexer-and-switch module 174. The duplexer-and-switchmodule 174 can include a duplexer to accommodate the full duplextransmission of CDMA systems as well as include a multiple outputswitch/filter for GPS, DBS, and/or possibly other systems and/orstandards incorporated in the MMR system 200. The duplexer-and-switchmodule 174 will typically route one set of bands to a first port (notshown), and a second set to a second port (not shown), thus acting as athree port device (e.g., the antenna port handling all frequencies, areceive port handling receive signals for provision to the MMR system200, and a transmit port handling transmit frequencies. In oneembodiment, the operation of the duplexer-and-switch module 174 iscontrolled by a control signal from the baseband subsystem 130 (e.g.,via connection 134). In other embodiments, a switch (e.g., controlledfrom the baseband subsystem 130 via connection 134, for example) can beused to route received signals to the MMR system 200 or transmit signalsfrom connection 162 to the antenna 172.

Signals received by antenna 172 will, at the appropriate time determinedby baseband system 130, be directed via the duplexer-and-switch module174 to the MMR system 200 via connection 173. As will be described infurther detail below, the MMR system 200 switches operation between theCDMA mode and the DBS mode, among other modes, using the CDMA basebandarchitecture for the different modes. Thus, the MMR system 200 includescomponents used for receiving and processing (e.g., filtering,downconversion, amplification, demodulation, etc.) signals for thevarious modes. The MMR system 200 provides output signals overconnection 198 to the bus 128 for further processing in the digitaldomain.

FIG. 2 is a block diagram illustrating one embodiment of an MMR systemusing an analog baseband system. In particular, shown is the MMR system200 a implemented with an analog baseband system. The MMR system 200 aincludes functionality for receiving and processing signalscorresponding to several modes via connection 173. Connection 173includes processing paths corresponding to the CDMA, GPS, PCS, and DBSmodes. The path starting at connection 201 from the duplexer-and-switchmodule 174 corresponds to a signal-processing path for the CDMA mode.The path starting at connection 233 represents a signal-processing pathcorresponding to the GPS mode. The path starting at connection 253corresponds to a signal-processing path for the PCS mode. The pathstarting at connection 267 corresponds to a signal-processing path forthe DBS mode. A common baseband section 212 a provides for a commonarchitecture providing baseband signal-processing of signals from thevarious signal-processing paths.

Beginning with the CDMA signal-processing path, the signal received fromthe duplexer-and-switch module 174 is provided over connection 201 to aduplexer 202. The duplexer 202 filters the received signal and suppliesthe filtered signal on connection 203 to CDMA low noise amplifier (LNA)204. The duplexer 202 can be a bandpass filter, which passes allchannels of the particular cellular system in which the portabletransceiver 100 (FIG. 1) is operating. As an example, in an 800 MHz CDMAsystem, the receive section of a duplexer 202 passes substantially allfrequencies from approximately 869.64 MHz to 893.97 MHz, with channelsspaced 30 kHz from each other. One purpose of the duplexer 202 is toreject all frequencies outside the desired frequency region. The CDMALNA 204 amplifies the weak signal on connection 203 using amplifiers 206a and/or 206 b, and provides the amplified signal over connection 205 toa CDMA Surface Acoustic Wave (SAW) filter 208. The CDMA SAW filter 208rejects unwanted signals (e.g., transmitter signal leakage) and providesthe filtered signal over connection 207 at a defined frequency to thedownconverter 210 (labeled “mixer” in FIG. 2).

The downconverter 210 receives a local oscillator signal or LO, fromPhase-Locked Loop (PLL) element 290. In one embodiment, the PLL element290 includes an oscillator 246, divide-by-N 248 (where N is an integernumber that is adjusted depending on the different channel numbers forthe different systems), loop filter 250, and reference crystaloscillator 252. Within each standard such as CDMA or PCS, N variesdepending on the channel number. For the DBS case, there is only onecenter frequency and hence N remains fixed. N can also be a fractionalnumber (e.g., non-integer) depending on the system requirementscorresponding to different standards. Thus, the value of N can change ina given system or mode to tune across different channels. The PLLelement 290 signal instructs the downconverter 210 via connection 243 asto the proper frequency to which to downconvert the signal received fromthe CDMA SAW filter 208. The signal on connection 207 is thusdownconverted to baseband on connection 209 (carrying the “I” signal)and 221 (carrying the “Q” signal).

The common baseband section 212 a provides for filtering, DC (directcurrent) offset correction, and amplification of the “I” and “Q” signalsof the various signal paths. The common baseband section 212 a includeslow-pass (LP) filters 214, 228, all-pass (AP) filters 226 and 238, DCcorrection elements 224 and 236, and automatic gain control (AGC)element 216. As explained below, the LP filters 214, 228 (and LP filters220 and 232 of the AGC element 216) and DC correction elements 224 and236 of the common baseband section 212 a are adjustable (e.g., haveswitchable bandwidths via control signals from the baseband subsystem130, FIG. 1) to achieve the desired frequency response for theparticular mode being implemented (e.g., CDMA, PCS, GPS, DBS). Forexample, the 3-dB bandwidths for the CDMA, GPS, and DBS modes areapproximately 630 kHz, 1 MHz, and 8 MHz, respectively. Thus, each of theLP filters 214, 228, 220, and 232 operate under a control input thatchanges the resistance and/or capacitance of the filter based on thedesired bandwidth while minimizing the impact of filter noise. Further,the difference in DC bandwidth correction can be fifty-fold betweenvarious systems (e.g., approximately 1 kHz for CDMA versus 50 kHz forDBS), and thus the DC correction elements 224 and 236 are adjusted in asimilar manner.

Since DBS systems are similar in nature to CDMA systems in terms of thephysical layer signal characteristics (e.g., the waveforms in bothsystems are direct sequence spread spectrum systems), several of theCDMA receiver functional blocks (or rather the components therein) canbe leveraged to integrate the DBS functionality with the CDMAarchitecture. This approach of reusing and sharing the functional blocksbetween CDMA and DBS provides a low-cost architecture in terms ofexternal components, die size and total system cost. The low-pass filtercut-off frequency (LP filters 214, 228, 220, and 232) as well as theDC-offset loop corner cut-off (224 and 238) are switched between CDMAand DBS modes. The low-pass cut off frequency refers to the extent ofthe signal bandwidth (BW) for both modes (e.g., CDMA and DBS), forexample. Since both CDMA and DBS systems are wideband systems and havenegligible energy near DC, DC-offset loops can function as high-passfilters that have a high-pass cut-off frequency. In the case of CDMA,the −3 decibel (dB) cut-off of the low-pass filter is approximately 630kilo-Hertz (kHz) and the high-pass corner is approximately 1 kHz. Whenthe MMR system switches to the DBS mode, the low-pass filter cut off isswitched to approximately 8.192 MHz and the high-pass corner is switchedto approximately 20-50 kHz. Hence, the DC cut-off frequency can beswitched between values, for example by switching capacitors or othercircuit elements. The same VGAs (218 and 220) are used for the CDMA andDBS systems since the dynamic range requirements in the DBS case at theupper end is limited by the repeater distance and near field effects.

The “I” baseband signal on connection 209 corresponding to thedownconverted CDMA signal is filtered by LP filter 214, and providedover connection 211 to automatic gain control (AGC) element 216. The “Q”signal on connection 221 corresponding to the downconverted CDMA signalis similarly filtered by LP filter 228, and provided over connection 223to AGC element 216. The AGC element 216 includes variable-gainamplifiers (VGAs) 218 and 222 (in the “I” path), and 230 and 234 (in the“Q” path). The AGC element 216 also includes LP filters 220 in the “I”path and 232 on the “Q” path. The “I” and “Q” signals are amplified andlow-pass filtered, and the processed “I” and “Q” signals are providedover connections 217 and 229 respectively.

The processed “I” signal on connection 217 undergoes DC correction viathe DC correction element 224. The DC corrected “I” signal is subject tofiltering at AP filter 226, and the filtered signal is provided overconnection 198 to the baseband subsystem 130 (FIG. 1) for furthersignal-processing. The processed “Q” signal similarly undergoes DCcorrection at DC correction element 236 and filtering at AP filter 238.DC correction elements 224 and 236 are also bandwidth-adjusted based onthe implemented mode, similar to that described for the LP filters ofthe common baseband section 212 a. The filtered signal is provided overconnection 198 to the baseband subsystem 130 for furthersignal-processing. The signal(s) on connection 198 can be provided to ananalog-to-digital converter (ADC) (not shown) in the baseband subsystem130 (FIG. 1). The ADC can provide the converted signal to othercomponents of the baseband subsystem 130 via the bus 128 or to othercomponents. For example, the signal can be digitized (e.g., at the ADC)and provided to the DSP 124 (FIG. 1), microprocessor 118 (FIG. 1), or amodem (not shown), etc., depending on the application.

GPS signals are received from the duplexer-and-switch module 174 onconnection 233 and filtered at pre-select filter 240. The pre-selectfilter 240 can reject substantially all other frequencies beyond the GPSsignal band. The resultant signal provided at the selected frequency isprovided on connection 235 and amplified at amplifier 242. The amplifiedsignal is provided at connection 237 to the GPS downconverter 244.

The PLL element 290 signal instructs the GPS downconverter 244 viaconnection 243 as to the proper frequency to which to downconvert theamplified signal on connection 237. The downconverted signals (“I” and“Q”) are provided on connections 239 and 241 respectively, passed to thecommon baseband section 212 a, and processed based on the filtersettings and the DC-offset correction provided via control signalsprovided from the baseband subsystem 130 (e.g., via connection 134, FIG.1). In other words, filters (e.g., 214, 228, 220, 232) and the DCcorrection elements 224 and 236 of the common baseband section 212 a areadjusted by the baseband subsystem 130 to provide the proper frequencyresponse for the selected mode (e.g., CDMA, GPS, etc.).

PCS signals are received at the duplexer 254 from theduplexer-and-switch module 174 over connection 253, and provided to thePCS LNA 256 via connection 255. The PCS LNA 256 includes amplifiers 258a and 258 b. The selected PCS signals are provided over connection 257to the PCS RF SAW filter 260, which selects out the desired frequency ina manner similar to that described for the CDMA SAW filter 208. Thesignal at the selected frequency is provided over connection 259 to thePCS downconverter 262, where it is downconverted to baseband under thecontrol of PLL element 290 via connection 243. The baseband signals areprovided over connections 261 and 265 to the common baseband section 212a for processing as described above. The LP Filters and DC correctionelements are adjusted corresponding to the PCS mode, as described above.

The DBS signal-processing path includes a DBS preselect filter 264, DBSLNA 266, and DBS downconverter 268. A separate LNA 266 and downconverter268 may be used to accommodate the different RF frequencies and no RFSAW filter is required at least in part because a direct conversionarchitecture is employed in one embodiment for the DBS portion of theMMR system 200 a and there is no image frequency. Further, there is notransmission to the satellite and hence there is no full duplexoperation like the CDMA system. The DBS signal is received at the DBSpreselect filter 264 from the duplexer-and-switch module 174 overconnection 267. The DBS LNA 266, as is true for the like-component shownin FIGS. 4 and 5, can include a bypass mode in order to bypass the DBSLNA 266 at high signal strengths, especially when the transceiver 100(FIG. 1) is disposed in close proximity to a ground repeater. Thefiltered signal is provided over connection 269 to the DBS LNA 266. TheDBS LNA 266 amplifies the signal if necessary, and the signal is thenprovided to the DBS downconverter 268 via connection 271. The DBSdownconverter 268 receives an LO signal from the PLL element 290 overconnection 243 to downconvert signals received over connections 271 tobaseband. The “I” and “Q” signals provided by the DBS downconverter 268are provided over connections 273 and 275 to the common baseband section212 a, in a manner similar to that described above for the othersignal-processing paths. In other embodiments, the DBS downconverter 268can be omitted and one of the downconverters of the other systems (e.g.,the PCS downconverter 262) can be used for performing downconversion ofthe DBS-based signal. Also as described above, the LP filters and DCcorrection elements are adjusted based on the selected mode.

FIGS. 3A-3B are graph diagrams illustrating the different low-passfilter characteristics required for the embodiment shown in FIG. 2 forthe CDMA and DBS modes. As indicated above, the LP filters 214, 220,228, and 232 (FIG. 2) are adjusted via signals received from thebaseband subsystem 130 (FIG. 1). FIG. 3A represents the LP filtercharacteristics for the CDMA mode, and FIG. 3B represents the filtercharacteristics for the DBS mode. Referring to FIGS. 3A and 3B, they-axis 302 provides an indication of the normalized amplitude level ofthe processed signal in units of dB, and the x-axis 304 provides anindication of the signal frequency in units of kHz. Point 306 on they-axis 302 represents the normalized amplitude level of the signalresponse, and point 308 represents that the attenuation of the filter(normalized amplitude) at a particular offset frequency is finite anddoes not reach infinity. Referring to FIG. 3A, the cut-off frequency (−3dB frequency) for the CDMA mode is shown at point 310, which correspondsto approximately 630 kHz. Signals are passed up until approximately 900kHz, as represented by point 312. For the DBS frequency response, point314 represents the −3-dB cut-off frequency, which corresponds to 8.192MHz. Signals are passed in the DBS mode up until approximately 11.63MHz, as represented by point 316. Thus, when the cut-off frequency isswitched from the CDMA system to the DBS system, the shift factor of thefilter remains the same. The shift factor is a ratio of passbandfrequency to stop band frequency. For example, in a CDMA system, thepassband frequency can be 630 kHz and the stop band frequency can be 900KHz. The same or similar ratio can applied to DBS passband and stop bandas well.

FIG. 4 is a block diagram illustrating a second MMR system embodimentconfigured with a digital baseband system. The components correspondingto the signal-processing paths upstream of and including thedownconverters for each signal-processing path are the same orsubstantially similar to that described for the MMR system 200 a of FIG.2, and thus the corresponding explanation will be omitted for clarity.“I” and “Q” baseband signals from the downconverters corresponding tothe CDMA, GPS, PCS, and DBS signal-processing paths are provided to acommon baseband subsection 212 b. The common baseband subsection 212 bincludes LP filters 414 and 436, VGAs 416 and 438, DC correctionelements 418 and 440, analog-to-digital converters (ADCs) 420 and 442(e.g., sigma delta converters), and decimator filters 422 and 444(represented by a downward arrow followed by an upper-case M). Thecommon baseband section 212 b also includes finite-impulse responsefilters (FIRs) 424 and 446, digital to analog converters (DACs) 428 and432, and smoothing filters (SF) 430 and 434.

Processing of the “I” signal will be described, with the understandingthat a similar explanation for processing of the “Q” signal applies. The“I” signal is filtered at the LP filter 414 and provided on connection411. As described for the analog embodiment of FIG. 2, the LP filter 414(and 436) and the DC-offset correction element 418 (and 440) arebandwidth adjusted (e.g., have switchable bandwidths via, for example,control signals from the baseband subsystem 130, FIG. 1) to achieve thedesired frequency response for the particular mode being implemented(e.g., CDMA, PCS, GPS, DBS). The same or similar bandwidth adjustmentsare implemented for like-components of the embodiment illustrated inFIG. 5. The filtered signal provided on connection 411 is amplified byVGA 416 and provided on connection 413. Note that the functionality ofthe VGA 416 (and corresponding VGA for the “Q” signal) can be performedpost-decimation (described below) in some embodiments, and/or thefunctionality can be integrated into the ADCs (e.g., ADC 420) in otherembodiments. The amplified signal on connection 413 undergoes DC-offsetcorrection at DC correction element 418. The DC corrected signal isprovided to the ADC 420, where it is sampled corresponding to thesampling rate designated by one or more components of the basebandsubsystem 130 (FIG. 1, for example, the DSP 124). The ADC 420 and 442can thus be shared among the various modes with a change in the samplingclocks.

For example, the sampling clock of the ADC 420 is switched based on theselected mode, such that a different sample rate may be used for theCDMA mode than is used for the DBS mode. An example would be where theCDMA sampling clock is 9.6 MHz or 19.2 MHz that provides anover-sampling ratio approximately equaling 8 and 16 respectively.Alternatively, the sampling clock may be chosen to be an integermultiple of the chip rate which is 1.2288 MHz. The sampled signal issent over connection 417 to the decimator filter 422, which downsamplesfrom a higher frequency to a lower frequency.

Decimation is an operation of downsampling from a higher frequency to alower frequency. It could be an integer rate conversion or a non-integerrate conversion. Decimation is then performed to a lower rate thatequals either the Nyquist sampling rate or a multiple of the same.Hence, the decimation factor would equal 4 or 8 for the above-describedsampling clock frequencies of 9.6 MHz and 19.2 MHz respectively.Decimation can occur to a different sampling value for the various modes(e.g., CDMA versus DBS). Thus, the decimator filter 422 (and 444) canhave its sampling rate adjusted to achieve the desired decimation (e.g.,via a control signal from the baseband subsystem 130, FIG. 1). In theDBS mode, the sampling clock chosen can equal a multiple of the chiprate, for example 16.384 MHz. Therefore, this would result in a samplingclock of 131.072 MHz/65.536 MHz that results in an over-sampling ratioof 8 and 4 respectively. Similar decimation factors can be employed inorder to convert the output to a lower rate before feeding the digitalfilters.

The sampled value provided from the decimator filter 422 is providedover connection 419 to the FIR filter 424. The FIR filter 424 (and 446)is also a component that is adjusted based on the mode of the signalreceived and processed. The filtered signal is provided over connection421 to the DAC 428, where it is converted to an analog signal andprovided over connection 423. The DAC 428 includes a sampling rate thatalso is adjusted based on the mode implemented. The sampling rate of theDAC 428 is generally equal to or proportional to the sampling rateimplemented by the decimator filter 422. The signal provided overconnection 423 is further filtered (e.g., removing alias spurs createdby the sample and hold operation performed by the DAC 428) at thesmoothing filter 430, and then provided over connection 198. Thus, thecommon baseband section 212 b can process signals received in any of themodes (e.g., CDMA, GPS, PCS, or DBS) using shared components, some ofwhich are adjusted to accommodate the various frequency responses forthe respective mode.

FIG. 5 is a block diagram illustrating a third MMR system embodimentusing a second digital baseband system. The third MMR system embodiment200 c shown in FIG. 5 is substantially similar to the second MMR systemembodiment 200 b. However, the third MMR system embodiment 200 c differsfrom the second MMR system embodiment 200 b in that the third embodiment200 c omits the DACs 428 and 432 and the smooth filters 430 and 434 ofFIG. 4. Similar to the second MMR system embodiment 200 b, the third MMRsystem embodiment 200 c has a sampling rate that is switched (e.g., viaADC 420) between CDMA and DBS modes to accommodate a commonarchitecture. Further, the decimator filters 422 and 444 and FIR filters424 and 446 are adjusted between the two modes. Such adjustments infilter response and/or sampling rates can be implemented viaread-only-memory (ROM) code in memory 120 (or microprocessor 118 or DSP124) or dynamically adjusted (e.g., real-time processing). Also, thelow-pass filters and DC-correction elements are adjusted as explained inassociation with FIG. 4.

The sharing of the high dynamic range ADC's between the CDMA and DBSmodes, wherein the ADCs (e.g., ADCs 420 and 422, FIG. 4) are configuredas sigma-delta architectures (specialized ADCs), can be designed toconsume lower power when operating at the lower sampling rate, while inthe DBS mode, the power may be higher. This can be handled by switchingoperations in additional stages to achieve the dynamic range possiblyrequired in DBS mode.

While various embodiments of the invention have been described, it willbe apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible that are within the scopeof this invention. Accordingly, the invention is not to be restrictedexcept in light of the following claims and their equivalents.

1. A method for receiving signals based on a plurality of systems, themethod comprising: converting a first signal based on a first system toa first baseband signal; converting a second signal based on a secondsystem to a second baseband signal; processing the first baseband signalusing baseband components; and processing the second baseband signalusing the baseband components.
 2. The method of claim 1, wherein thefirst system and the second system each include at least one of thefollowing systems code-division multiple access, personal-communicationservice, global-positioning satellite, digital-broadcast satellite, andglobal system for mobile communications.
 3. The method of claim 1,wherein the processing includes at least one of filtering, amplifying,providing digital-to-analog conversion, providing analog-to-digitalconversion, sampling, and correcting for direct current (DC) offset. 4.The method of claim 1, wherein the processing includes processing in atleast one of a digital domain and an analog domain.
 5. The method ofclaim 1, wherein the processing includes configuring at least one of thebaseband components for a first frequency response characteristic forthe first baseband signal and configuring the at least one of thebaseband components for a second frequency response characteristic forthe second baseband signal.
 6. The method of claim 5, wherein the atleast one of the baseband components include at least one of low-passfilters, finite-impulse response filters, and DC-offset correctionelements.
 7. The method of claim 1, wherein the baseband componentsinclude at least one of low-pass filters, all-pass filters,variable-gain amplifiers, analog-to-digital converters,digital-to-analog converters, finite-impulse response filters, smoothingfilters, decimator filters, and DC-offset correction elements.
 8. Themethod of claim 1, wherein the converting and processing are performedfor a plurality of signals from a plurality of systems.
 9. The method ofclaim 1, wherein the processing includes sampling at a first samplingrate for the first baseband signal and a second sampling rate for thesecond baseband signal.
 10. The method of claim 9, wherein the samplingis performed by at least one of a decimator filter, a digital-to-analogconverter, and an analog-to-digital converter.
 11. A multi-mode receiversystem for processing signals based on a plurality of systems,comprising: a baseband section configured to process a first basebandsignal based on a first system using baseband components, wherein thebaseband section is further configured to process a second basebandsignal based on a second system using the baseband components.
 12. Thesystem of claim 11, further including a downconverter that is configuredto convert a first signal to the first baseband signal and a secondsignal to the second baseband signal.
 13. The system of claim 11,further including a first downconverter and a second downconverter, thefirst downconverter configured to convert a first signal to the firstbaseband signal, the second downconverter configured to convert a secondsignal to the second baseband signal.
 14. The system of claim 11,wherein the first system and the second system each include at least oneof the following systems code-division multiple access,personal-communication service, global-positioning satellite,digital-broadcast satellite, and global system for mobilecommunications.
 15. The system of claim 11, wherein the basebandcomponents include at least one of low-pass filters, all-pass filters,variable-gain amplifiers, analog-to-digital converters,digital-to-analog converters, finite-impulse response filters, smoothingfilters, decimator filters, and DC-offset correction elements.
 16. Thesystem of claim 11, wherein at least one of the baseband components areconfigured for a first frequency response characteristic for the firstbaseband signal and configured for a second frequency responsecharacteristic for the second baseband signal.
 17. The system of claim16, wherein the at least one of the baseband components include at leastone of low-pass filters, finite-impulse response filters, and DC-offsetcorrection elements.
 18. The system of claim 11, wherein at least one ofthe baseband components is configured to sample at a first sampling ratefor the first baseband signal and a second sampling rate for the secondbaseband signal.
 19. The system of claim 18, wherein the at least one ofthe baseband components includes at least one of a decimator filter, adigital-to-analog converter, and an analog-to-digital converter.
 20. Thesystem of claim 11, wherein the baseband section is further configuredto process a plurality of signals from a plurality of systems.
 21. Atransceiver, comprising: means for transmitting signals; means forreceiving signals, wherein the means for receiving includespre-converting processing means; means for converting a first signalbased on a first system to a first baseband signal; means for convertinga second signal based on a second system to a second baseband signal;and means for processing the first baseband signal, wherein the meansfor processing the first baseband signal is used for processing thesecond baseband signal.
 22. The transceiver of claim 21, wherein thefirst system and the second system each include at least one of thefollowing systems code-division multiple access, personal-communicationservice, global-positioning satellite, digital-broadcast satellite, andglobal system for mobile communications.
 23. The transceiver of claim21, wherein the means for processing includes at least one of means forfiltering, amplifying, providing digital-to-analog conversion, providinganalog-to-digital conversion, sampling, and correcting for directcurrent (DC) offset.
 24. The transceiver of claim 21, wherein the meansfor processing includes means for processing in at least one of adigital domain and an analog domain.
 25. The transceiver of claim 21,wherein the means for processing includes means for providing a firstfrequency response characteristic for the first baseband signal and asecond frequency response characteristic for the second baseband signal.26. The transceiver of claim 21, wherein the means for processingincludes means for sampling at a first sampling rate for the firstbaseband signal and a second sampling rate for the second basebandsignal.
 27. The transceiver of claim 21, wherein the means fortransmitting, means for receiving, means for converting, and means forprocessing are performed for a plurality of signals from a plurality ofsystems.
 28. A multi-mode receiver system, comprising: a code-divisionmultiple access system having a common baseband system; and adigital-broadcast system that shares the common baseband system with thecode-division multiple access system.
 29. The multi-mode receiver systemof claim 28, wherein the common baseband system includes at least one ofa low-pass filter, an all-pass filter, a direct current (DC)-correctionelement, and a variable-gain amplifier.
 30. The multi-mode receiversystem of claim 29, wherein the low-pass filter and the DC-correctionelement are configured to include switchable bandwidths.
 31. Themulti-mode receiver system of claim 28, wherein the common basebandsystem includes at least one of a low-pass filter, an analog-to-digitalconverter, a decimator filter, a digital-to-analog converter, asmoothing filter, a finite-impulse response filter, a direct current(DC)-correction element, and a variable-gain amplifier.
 32. Themulti-mode receiver system of claim 31, wherein at least one of theanalog-to-digital converter, the digital-to-analog converter, and thedecimator filter is configured to have a first sampling rate for thecode-division multiple access system and a second sampling rate for thedigital-broadcast system.
 33. The multi-mode receiver system of claim31, wherein at least one of the finite-impulse response filter, theDC-correction element, and the decimator filter is configured to operateat a first frequency response for the code-division multiple accesssystem and a second frequency response for the digital-broadcast system.